I sold my D70s (with the 18-70) on ebay for a reasonable price 2 days ago, having not really been satisfied with it. I had it for about half a year, but found myself using the outstanding compact camera Konica Minolta Dimage A2 more often than the D70s.
While the D70s's image quality surpassed that of the A2 by quite a margin, its flexibility, ergonomics made me opt for the A2 most of the time. It's a lot lighter and smaller, offers quite a few more functions, doesn't have any dust problems, has anti shake (which compensates for the lack of usable high isos a little), a great menu system, a really nice EVF and a lens which offers just the right range for me.
So, why should I get a new DSLR? The thing is, I'm not really that happy with the A2's image quality. It's pretty good for a compact and quite acceptable when RAW is used, but having seen what the D70s was capable of producing, it does pale in comparison. Perhaps though, just keeping the A2 would be the most convenient option. An E-510 might solve quite a few of the problems I had with the D70s while offering superior image quality, but it is pretty expensive, and I'm not really sure whether I would get into the menu system or miss the EVF.
I have also been considering either buying an old Maxxum/Dynax 7D or a Sony Alpha, but since they seem to fail quite often, I have gone off that option a bit. Also, they would not solve my dust problem, and that was a big annoyance with the D70s and also be bigger than the E-510. They would be quite a bit cheaper than the E-510 though and have the menu system and ergonomics I like so much about the A2.
Well, I can't really decide...

The E-510 will certainly give you anti-shake, but then so would a VR lens on your Nikon.

Dust is a problem with all DSLRs, although the Olympus system appears to do a better job at getting rid of it - or at leats making it harder to spot.

So if you're after a small, light DSLR with anti-shake and decent anti-dust, then the E-510 certainly looks like one of your best bets, but you have to weigh up if you'll miss the benefits of a super-zoom like the smaller package with a massive optical range, movie mode and on-screen composition. Live View on the E-510 is neat, but nowhere as quick as a non-DSLR.